Upper Union River 
Amherst, Mariaville, Great Pond Plantation 
Description: 
A 13-mile reach of the West Branch of the Union River, beginning in Great Pond and 
extending downstream to Graham Lake supports habitat for rare animal species because its waters 
are undammed and largely unimpaired by activities in the surrounding uplands. The focus area 
supports healthy populations of the brook floater. The brook floater is a globally rare mussel 
species that inhabits free-flowing freshwater streams and rivers. Wood turtles also inhabit the 
Union River. These turtles overwinter in well-oxygenated flowing water and may utilize adjacent 
wetlands for feeding and adjacent uplands for feeding and nesting. The ribbon snake has also 
been documented within the focus area. This species typically inhabits vegetated wetlands and 
waterways with abundant amphibian populations (its most common food source). 
In addition, a small population of the pale green orchis (Platanthera flava) was found on 
the east bank of the Union River in Mariaville in 1997. 
Rare Species and Exemplary Natural Community Table for Union River 
Common Name 
Latin Name 
S-RANK 
G-RANK 
State 
Status 
Rare Plants 
Pale green orchis Platanthera flava v. herbiola S2 G4 SC 
Rare Animals 
Brook Floater Alismodonta varicose S3 G3 SC 
Ribbon Snake Thamnophis sauritus S3 G5 SC 
Wood Turtle Clemmys insculpta S4 G4 SC 
Other Habitats Mapped by MDIFW: 
Waterfowl / Wading Bird Habitat 
Conservation Considerations: 
• Degradation of free-flowing aquatic habitat (e.g damming, channelization, flow diversion 
or watershed disturbance) is one of the greatest causes for the loss of riverine aquatic 
species like freshwater mussels and wood turtles. Care should be taken to avoid 
alterations to the natural hydrological regime within, and upstream of, the focus area. 
• Degradation of water quality by inorganic and organic pollutants from point and nonpoint 
sources has the capacity to devastate sensitive aquatic species. One way to limit 
impact from erosion and siltation caused by activities such as logging in the watershed is 
to establish riparian buffers. Wider buffers, with as little alteration as possible within 
250’ of the wetland/upland border, provide better protection for riparian species. 
• Introduction of exotic species (such as introduced fish species) may affect potential host 
fish populations for mussels in the river and thereby limit the reproductive success of 
mussels. 
Protection Status: 
Aside from 870 acres of protected land around the perimeter of Great Pond, the remainder of the 
West Branch of the Union River is in private ownership.